Wireless Wiring for Radios (Oct, 1947)

Printed circuit boards are one of those things we’re so used to the you never really think about how people made electronics before them.

Wireless Wiring for Radios
THAT repairman’s headache, the jumble of wires on the bottom of a radio, may join crystal sets in the museum. Two new processes mass-produce neat circuits, easy to check for trouble. They promise to do for average radios what printed circuits (PSM May ’46, p. 131) are doing for miniatures.

In a system invented by A. M. Hathaway and developed by Spraywire Labs, of Minneapolis, a plastic panel is covered by a Scotch-tape stencil of the circuit. Through this, grooves are sandblasted, then spray-gunned full of atomized metal. Two guns can spray more than 1,000 units an hour.
Another method uses two copper sheets on opposite sides of an insulating panel. All horizontal parts of the circuit are stamped out in strips on one side: vertical on the other. The two are connected by metal eyelets punched through the panel.

I’ve heard of up to SIX layer boards. One problem for the home-repair person who buys a soldering iron and “solder sucker” from Radio Shack (who used to carry 10X as many parts, including every type of transistor and common integrated circuit) is that they no longer user rivets to connect layers, but somehow plate the holes with solder tubes that can be damaged if you try an old school repair.

Sprayed metal?! That’s really really weird.

There’s computer software that automatically (more or less) lays out a design on paper into a physical design of a (usually two layer) board. But…if you look at certain products, you’ll notice that they’ve either failed to get the design to be flat, since it’s too complicated or, more often they made a MISTAKE and instead of re-doing all the boards, they have people use an X-acto knife to destroy a lead and then they manually solder little jumper wires between the corrected points, ha ha.

I have a fancy machine control board for my PC, and it has three jumpers and one extremely humorous kludge, in which a mere two leads of an eight pin IC chip have been physically cut and little 1/16″ long yellow insulated wires have been soldered into a cross, to change which solder pads leads to which IC pins. Oops!

I make my own lamp dimmers. I have a computer controlled routing machine, so I just have it first physically cut pre-copper-clad fiberglassed epoxy (G-10 or G-11) material, then have it drill lead holes and finally cut the fifty-at-a-time-from-a-six-inch-square separated PCBs out.

Then, since I’m manually “stuffing” parts, I use a special wire cutter available from places like Mouser.com which shears leads off at the same time it CRIMPS them into a space shape, so they hold in prior to soldering. Mass produced PCBs are soldered by being angled into then out of huge solder baths of molten lead alloy. I just use a miniature version of this called a “solder pot” that has a 1-2 inch wide cup that you feed thick solder into until you have it filled. I make a custom mix of two different solder resins (since I’m not using “rosin core”) solder like you get at Radio Shack to dip them into first, or the solder wont wet the metal well. One is very thin (residue free) but not vigorous enough, so I mix in a little “real” stuff. Amen.